Biopharmaceutical materials are often held in single-use bulk storage containers such as plastic bags or other flexible containers. Such single-use containers or bags are commonly drained by gravity through a port located on the bottom of the bag. Although this method is effective in recovering product from the container, it has some disadvantages. Large capacity bags (here defined as 50 L or greater) are commonly handled as bag-in-box systems (e.g, a flexible container in a more rigid structure) since the bag is generally not self-supporting and requires protection against damage. Installation of a bottom drain in a bag-in-box structure requires that an operator manipulate a drain line of the bag such that it passes from the inside of the box to the outside of the box. The drain line may then be located outside the protective structure of the box and may be damaged during transportation and handling. A bottom port may be also be damaged by a combination of improper installation and hydrostatic pressure. Furthermore, if containment is desired in the event of a leak in the bag, then the hole in the box creates a path for leakage into the surrounding environment.
Various systems are known for draining a single use bag through a port located on the top of the bag. If no dip tube is provided then the flexible bag walls of such a container usually collapse and block flow, thereby preventing full recovery of the fluid inside. It is possible in some cases to manipulate the bag during the draining process in order to reduce the risk of blockage (and minimize the amount of liquid which is not recovered or the “holdup volume”), but this requires manual intervention and creates an “accordion” with many random folds and unreliable performance. A dip tube may be run from the drain port located at the top of the bag down to the bottom of the bag. However, this approach is problematic for several reasons. First, the flexible bag wall commonly collapses over the end of the dip tube and thereby prevents full recovery of the fluid inside. Also, if the end of the dip tube drifts away from the bottom of the bag then it may become trapped between collapsing bag walls, thereby preventing full recovery of the fluid inside.
Thus, there is a need for systems and methods for storing biopharmaceutical materials, which minimize a hold up volume of liquid in containers holding such materials and facilitate evacuation of the containers.